Self-healing behavior of Sc₂Si₂O₇/SiC composites for environmental barrier coatings

The high-temperature oxidation and self-healing behavior of promising environmental barrier coating material Sc₂Si₂O₇ containing 10 vol% SiC dispersed nanoparticles is reported for oxidation times up to 10 h at temperatures of 1100 and 1300°C. Sc₂Si₂O₇/SiC nanocomposites were prepared by spark-plasma sintering. Artificially induced surface cracks did not fully recover after 10 h at 1100°C but did fully recover after heat treatment at 1300°C for 5 h in air. The mechanism of self-healing is attributed to the volume expansion resulting from oxidation of SiC to SiO₂ at elevated temperature. The oxidized zones within the composites were confirmed to be thicker after heating at 1300°C than at 1100°C, their depths following a parabolic rate law with constants of 6.2 × 10^-11 and 1.9 × 10^-12 m²/s, respectively. The results show that Sc₂Si₂O₇/SiC nanocomposites exhibit self-healing properties, and thus may be attractive for propulsion applications when considering their lower specific gravity and good corrosion resistance.